Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.41	4.811%	$155.55	$155.55	$155.55	$155.60
Purchase #2	$58.65	11.367%	$65.3167	$65.32	$65.30	$65.30
Purchase #3	$221.32	9.112%	$241.4867	$241.49	$241.50	$241.50
Purchase #4	$204.50	12.240%	$229.5308	$229.53	$229.55	$229.50
Purchase #5	$120.94	7.832%	$130.412	$130.41	$130.40	$130.40
Purchase #6	$76.63	7.481%	$82.3627	$82.36	$82.35	$82.40
Purchase #7	$132.28	10.241%	$145.8268	$145.83	$145.85	$145.80
7 purchase totals =	$962.73		$1,050.4857	$1,050.49	$1,050.50	$1,050.50